Quality characteristics of cold-dried beef slices

Meat Science 155 (2019) 36–42

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Quality characteristics of cold-dried beef slices ⁎

T

Elif Aykın-Dinçer , Mustafa Erbaş Department of Food Engineering, Engineering Faculty, Akdeniz University, Antalya, 07058, Turkey

A R T I C LE I N FO

A B S T R A C T

Keywords: Cold drying Dried meat Quality Low temperature Air flow rate

In this study, salted and pasteurized beef slices were dried to approximately 40% water content at different low temperatures (10, 15 and 20 °C) and air flow rates (1, 2, 3 and 4 m/s) and the quality characteristics of the colddried beef slices were investigated. The TBARS values of cold-dried slices increased from 42.01 to 54.54 μmol MDA/kg with the increase in drying temperature and from 27.29 to 67.79 μmol MDA/kg with the increase in air flow rate indicating that low temperature and low air flow rate can help to avoid the lipid oxidation. Low drying temperature was also found to impact on the color of cold-dried slices. Additionally, it was determined that the microbiological quality of cold-dried slices decreased as the temperature increased from 10 to 20 °C and air flow rate increased from 1 to 4 m/s. Finally, the slices dried at 10 °C and 3 m/s had higher sensorial property scores. Consequently, low drying temperature and high air flow rate could enhance the quality of dried beef slices.

1. Introduction Drying is generally seen as the removal of water from a product with the principle of temperature and/or relative humidity difference, under hygienic conditions, and the reduction of water activity to control the microbiological, biochemical and chemical activity of the product (Krokida, Karathanos, Maroulis, & Marinos-Kouris, 2003; Petit, Caro, Petit, Santchurn, & Collignan, 2014; Rahman et al., 2005). After being salted using conventional methods, sun-dried or hot air-dried meats can be kept at room temperature for a few months. However, a prolonged drying process at high temperature may cause adverse changes in the chemical composition, structure and physical properties of the product and reduce the acceptability of the meat by the consumer (Calicioglu, Sofos, Samelis, Kendall, & Smith, 2003; Laopoolkit & Suwannaporn, 2011). The Maillard reaction, which is defined as a non-enzymatic browning reaction, affects the color of the dried meat products and occurs between the carbonyl groups of reducing sugars and free amino acids in the muscle during the drying period (Suryati, Astawan, Lioe, Wresdiyati, & Usmiati, 2014). The ribose is a reducing sugar and closely related to the degree of browning in dried meat products (Geng et al., 2015). It has also been reported that amino groups within a protein or peptides could participate in the Maillard reaction (Liu, Liu, He, Song, & Chen, 2015; Song et al., 2016). Besides the color of dried meat, Maillard reaction products also affect its texture, flavor and nutritional value (Geng et al., 2015; Nathakaranakule, Kraiwanichkul, & Soponronnarit, 2007). In addition, color development in dried meat products has been

⁎

associated with the amount of myoglobin in the meat (Aristoy & Toldrá, 1998; Pérez-Alvarez, Sayas-Barberá, & Fernández-López, 1999; Toldrá, 2011). The high amount of myoglobin pigment in dried product positively affects the product color and hence the consumer preferences. In a study, as the drying temperature increased, more myoglobin loss was detected in meat samples (King & Chen, 1998). Therefore, the color of fresh meat can be maintained if drying process can be performed at low temperature (Kilic, 2009). The glycerides and phospholipids found in dry cured meat products are converted into free fatty acids by lipolysis and the resultant unsaturated fatty acids are more prone to oxidation reactions than saturated ones (Skibsted, Mikkelsen, & Bertelsen, 1998). Lipid oxidation in dried meat products causes the formation of a rancid taste and the loss of fat-soluble vitamins and pigments (Heldman, Lund, & Sabliov, 2006). Jin et al. (2010) reported that the total amount of free fatty acids in dried meat samples called bacon was higher than those of phospholipids. Irregular water and temperature changes in the food during drying cause irregular volume changes. Depending on these changes, important quality defects such as fractures and cracks can also be seen in food (Heldman et al., 2006). The texture of dried meat products is associated with the degree of drying and hence products dried intensively have a harder texture (Toldrá, 2011). Deng et al. (2014) and AykınDinçer and Erbaş (2018) reported that an intense and hard structure is formed due to moisture loss, protein denaturation and shortening of the fibers during meat drying. Although drying will reduce growth of pathogens and

Corresponding author. E-mail address: [email protected] (E. Aykın-Dinçer).

https://doi.org/10.1016/j.meatsci.2019.05.001 Received 28 January 2019; Received in revised form 17 April 2019; Accepted 1 May 2019 Available online 02 May 2019 0309-1740/ © 2019 Elsevier Ltd. All rights reserved.

Meat Science 155 (2019) 36–42

E. Aykın-Dinçer and M. Erbaş

the water, the number of vacuum applications was set to 40 and the duration of individual vacuum applications was set to 10 s and this practice helped reduce the pressure inside the dryer to 0.7 atm. Thus, the water was collected in the waste container under the dryer. Pasteurized beef slices were dried at different low temperatures (10, 15 and 20 °C) and air flow rates (1, 2, 3 and 4 m/s) in the same unit and the quality characteristics of the dried samples were investigated. The drying process was continued until the samples reached the values of moisture (≈ 40%) and water activity (≈ 0.90) where sensorial aspects and microbial content is considered as acceptable. The dried samples were stored in polyethylene packages at +4 °C until analyzed.

microorganisms that cause spoilage in foods, it cannot always provide food safety, and the remaining microorganisms can cause deterioration of the product and health problems in consumers (Heldman et al., 2006). For instance, in response to Salmonella and E. coli O157:H7 outbreaks linked to dried meat products, the Food Safety and Inspection Service of the United States Department of Agriculture (FSIS/USDA) has suggested heating meat to 71.1 °C before drying, to eliminate the risk of pathogens (Calicioglu et al., 2003; Calicioglu, Sofos, Samelis, Kendall, & Smith, 2002). For that reason, various treatments such as hot water, steam, steam-vacuum and high pressure are used for the pasteurization of meat before the drying process (Andrés, Adamsen, Møller, Ruiz, & Skibsted, 2006; Hochreutener, Zweifel, Corti, & Stephan, 2017; Trivedi, Reynolds, & Chen, 2007). In recent years, the tendency towards alternative drying technologies has increased in order to prevent all or a large part of the limitations encountered during the operation of current dryers and to obtain high-quality dried meat products. The cold drying process, which is one of the alternative technologies, is based on the principle of using cold and dry air in the drying process after the cold air is allowed to leave its moisture on a cooler surface at the entrance of the drying unit. The efficiency of the drying process depends on the air flow rate and the temperature and/or relative humidity difference between the product and the air (Petit et al., 2014). The cold drying process has a positive effect on the quality of the biological materials despite the long processing time. Especially for heat-sensitive foods, the cooling process is one of the food preservation techniques that prolongs shelf life and prevent spoilage (Kilic, 2009). In this study, beef slices loaded into a cold dryer were dried at different low temperatures (10, 15 and 20 °C) and air flow rates (1, 2, 3 and 4 m/s) after being pasteurized with hot steam and physico-chemical, microbiological and sensory quality characteristics of dried beef slices were determined.

2.3. Chemical and physical analysis The moisture content of dried beef slices was determined by drying the samples at 105 °C (Memmert UNB 500, Schwabach, Germany) and the pH values were measured with a digital pH meter (Hanna HI 2210, Woonsocket, RI, USA) after homogenizing 5 g of sample in 50 mL distilled water for 60 s with an ultra-turrax (IKA-T18, Staufen, Germany) according to the Association of Official Analytical Chemists method (AOAC, 2000). The water activity (aw) was measured at 25 °C with a water activity meter (AquaLab 4TE, Decagon Devices Inc., USA). The thiobarbituric acid reactive substances (TBARS) were determined according to the method of Lemon (1975) and expressed as μmol malondialdehyde (MDA)/kg of sample. Non-protein nitrogen (NPN) was determined according to the method of Kaban (2009) and the results were expressed as g/100 g of samples. Color parameters (L⁎, a⁎, b⁎) of cold-dried beef slices were measured at five different points on the sample surface by the CIELAB system using a CR-400 Chromameter (8 mm aperture; 2° observer) (Konica Minolta, Japan). The L* value represents the brightness of the samples, the a* value represents the red-green color value and the b* value represents the yellow-blue color value. The light source was a pulsed xenon lamp and the samples were measured using illuminant D65. The color device was calibrated by using its white ceramic plate before actual use. Calibration was completed after the illuminant lamp flashed three times. The weight loss of slices (given as percentage) was calculated by dividing the difference of the weight of the slices before and after they were dried by the weight of the slices before they were dried. The change in size of the slices was calculated by the difference of the length, width and thickness of the slices, measured with a caliper, before and after they were dried. The cutting force (N) and toughness (Nxs) values of cold-dried samples were determined with a TA.XT Plus Texture Analyzer (Stable Microsystems, UK) using Blade Set (HDP/BS) (Warner Bratzler, WB). The speed of probe, trigger force and load cell were 2 mm/s, 10 g and 50 kg, respectively. For analysis, five randomly selected slices were used (Aykın & Erbaş, 2016).

2. Material and methods 2.1. Raw material Longissimus thoracis et lumborum (Kauffman, Habel, Smulders, Bergstrom, & Hartman, 1990) muscles of 10 different beef carcasses were purchased from a well-known butcher (Veli Cengiz Meat Products Ltd.) in Antalya, separated from the fat and connective tissue and sliced to a length of 146.0 ± 15.2 mm, width of 56.0 ± 8.6 mm and thickness of 2.5 ± 0.4 mm. Dry salting (0.75%) was applied on both sides of the beef slices to provide the eating salinity (≈1.85%). The salt crystals (0.75 g NaCl) distributed uniformly to the surface of slices (100 g fresh meat) were dissolved in the water in the structure of the meat. Mohr's method was used to measure the salt content of final product (Kirk & Sawyer, 1991). The salted beef slices were kept at +4 °C for 1 h by reversing every 15 min to complete the salt diffusion before drying. Slices were randomly divided into 12 groups for different drying temperatures (10, 15 and 20 °C) and air flow rates (1, 2, 3 and 4 m/s). Five slices of five different carcasses were randomly taken and used for each group. All groups included 25 slices, and a total of 300 slices (25 slices × 12 groups) were dried for one replication. Two replications were carried out for all analyses, so a total of 600 slices (300 slices × 2 replications) were dried and analyzed.

2.4. Microbiological analysis For microbiological analysis, 10 g of sample was homogenized manually with 90 mL of peptone under aseptic conditions. Appropriate dilutions were prepared and inoculation was performed using the pour plate method. Total aerobic mesophilic bacteria (TAMB) were enumerated on plate count agar (PCA, Merck) incubated at 30 °C for 48 h. Total psychrophilic bacteria (TPB) were determined on PCA (Merck) after incubation at 7 °C for 10 days. Micrococcus and Staphylococcus were determined on mannitol salt phenol-red agar (MSA, Merck) following incubation at 30 °C for 48 h. Lactic acid bacteria (LAB) were enumerated on de Man Rogosa Sharpe agar (MRS, Merck) in anaerobic conditions (Aneorocult A, Merck) after 48 h at 30 °C. Enterobacteriaceae were determined on violet red bile dextrose agar (VRBD, Merck) after incubation at 30 °C for 48 h under anaerobic

2.2. Drying experiments In this study, a cold dryer (patent number: TR 2015/10273) was used to produce a dried meat product that was minimally treated and did not generate a risk for food safety (Aykın-Dinçer & Erbaş, 2019). The salted beef slices were firstly hung in this cold dryer and subsequently pasteurized and dried. For pasteurization, hot steam was applied so that the core temperature of the slices was 72 °C. The water formed on pasteurized slices and in the dryer, because of the steam used for pasteurization, was removed by applying a vacuum. For removing 37

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It has been reported that the moisture content and water activity of intermediate moisture food varies between 20% and 50% and 0.70 and 0.90, respectively (Huang & Nip, 2001). Accordingly, it was determined that the cold-dried slices in the present study were in the category of intermediate moisture food, and therefore more stable to microbial spoilage than fresh meat. In a similar study on dried chicken meat, the moisture (60%) and water activity (0.90) were not affected by a small increase in temperature (from 50 °C to 55 °C) because the drying-time was adjusted to standardize the moisture of the samples(Jiang, Xu, Zhao, Huang, & Zhou, 2016). Generally, higher temperature increases the effective water diffusivity and facilitates the migration of water. In another study on fish meat dried at low temperatures (4, 10, 15 and 20 °C), it was similarly determined that moisture, water activity and pH values were either not affected by the temperature (Kilic, 2009). It was also reported that pastırma varieties, a traditional Turkish dried meat product, were among stable foods with respect to shelf life, and their water activity values were between 0.84 and 0.92 (Akköse, Kaban, Karaoğlu, & Kaya, 2018). The average pH of cold-dried slices was determined as 5.74 that was below the upper limit of 6.0 determined for pastırma by the Turkish Food Codex Meat and Meat Products Notification (Anonymous, 2012). It was previously reported that pH value in meat slices dried at 50 °C was 5.40 under an air flow rate of 1.5 m/s (Chabbouh et al., 2011). It was determined that the pH of cold-dried slices decreased by 0.1 units compared to the pH (5.82) of salted fresh ones. This might be the result of the fact that drying concentrated the already lactic acid present in the fresh meat and some hydrolysis process released free amino groups.

conditions (Aneorocult A, Merck). Yeast and molds were enumerated on potato dextrose agar (PDA, Merck) after incubation at 25 °C for 5 days under aerobic conditions. The enumeration was performed in parallel Petri dish plates that contained between 30 and 300 colonies at the end of incubation. Data were represented as the log of colony forming units (cfu) per g of dried beef (Maqsood, Al Haddad, & Mudgil, 2016). 2.5. Sensory evaluation In the sensory evaluation, dried beef slices were identified with three-digit numbers and presented in a random order to eight panelists; they were Masters students in food science and were trained about sensory evaluation. Panelists evaluated the twelve samples, in a single session, with a stop of 10 min after the sixth sample, to avoid sensory fatigue. In addition, the same panelists were used for each replication. Panelists were included in the model as fixed effect along with treatment. Panelists evaluated the samples regarding their appearance, color, odor, flavor, tenderness and overall acceptability with a ninepoint hedonic scale (1: did not like at all, 9: liked very much) (Huang, Shiau, Liu, Chu, & Hwang, 2005). Before testing a new sample, the panelists were asked to consume water in order to neutralize the taste in mouth. 2.6. Statistical analysis Three different drying temperatures (10, 15 and 20 °C) and four different air flow rates (1, 2, 3 and 4 m/s) were selected as variables and experiments were designed according to a randomized complete block design with two replicates. The treatments were considered to be a fixed effect and replications were included in the model as a random effect. The data were tested by variance analysis, and significant means were compared with Duncan's multiple comparison test using SAS version 7 (SAS Institute Inc., Cary, NC, USA). The values are presented as mean ± standard error.

3.2. TBARS and NPN values of cold-dried beef slices Lipid oxidation and protein breakdown are the main factors affecting the quality characteristics of meat products and determined by measuring TBARS and NPN values, respectively. TBARS and NPN values of cold-dried slices are given in Table 1. While the NPN value of cold-dried slices was not affected (P > .05), the TBARS value was significantly (P < .01) affected by drying temperature and air flow rate. The TBARS value of cold-dried slices increased due to an increase in temperature and air flow rate. Processing methods as well as the fatty acid profile of raw meat are highly effective on TBARS value of drycured meat products. This result might be due to the accelerating effect of relatively high temperature on the reaction kinetics and the intense exposure of samples to oxygen as air flow rate increased. These suggest low temperature and low oxygen can help to avoid the lipid oxidation. The oxidation of fatty acids occurs rapidly with increasing temperature. Gao, Yuan, Yu, and Liu (2016) found that the TBARS value of fish samples increased from 7.78 to 12.11 mg/kg by increasing the drying temperature from 5 to 35 °C. In another study on fish drying, a

3. Results and discussion 3.1. Moisture, water activity and pH values of cold-dried beef slices The moisture, water activity and pH values of cold-dried beef slices are given in Table 1. According to the results of variance analysis, the moisture content, water activity and pH values of cold-dried slices were not significantly affected (P > .05) by drying temperature and air flow rate. The average moisture content and water activity of cold-dried slices were 39.85% and 0.89, respectively. Moisture content provides information on food stability and is used for the classification of foods. Table 1 The physico-chemical properties of cold-dried beef slices ( ± standard error). Moisture (%)

Water activity

pH

TBARS (μmol MDA/kg)

NPN (g/100 g sample)

Temperature (T, °C, n = 8) 10 39.76a ± 0.13 15 39.88a ± 0.14 20 39.90a ± 0.23 Significance NS

0.89a ± 0.01 0.89a ± 0.01 0.90a ± 0.01 NS

5.71a ± 0.02 5.78a ± 0.04 5.73a ± 0.02 NS

42.01c ± 4.12 48.20b ± 7.47 54.54a ± 6.52 ⁎⁎

4.22a ± 0.09 4.29a ± 0.14 4.27a ± 0.04 NS

Air flow rate (A, m/s, n = 6) 1 39.72a 2 39.54a 3 40.10a 4 40.03a Significance NS T×A NS

0.89a 0.89a 0.90a 0.89a NS NS

5.71a 5.75a 5.75a 5.75a NS NS

27.29d 39.64c 58.28b 67.79a ⁎⁎ ⁎⁎

4.25a 4.20a 4.25a 4.34a NS NS

± ± ± ±

0.14 0.07 0.21 0.24

± ± ± ±

0.01 0.01 0.01 0.01

a,b,c,d

Means with different letters within the column indicate differences. NS Not Significant (P > .05). ⁎⁎ P < .01. 38

± ± ± ±

0.04 0.05 0.02 0.01

± ± ± ±

1.62 2.74 2.38 4.60

± ± ± ±

0.16 0.07 0.07 0.13

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by air flow rate, while b* value significantly increased (P < .01) with increasing air flow rate. This increase in the b* value, which leads to a color of dried beef slices from darkness to yellowness, may be due to the exposure of the dark pigments to more oxygen during drying and hence bleaching of their color. Xu, Zhu, Liu, and Cheng (2018) reported that there may be an increase in b* value as a result of oxidation of the ferrous ion.

lower TBARS value was determined at the drying temperature of 4 °C than at 10, 15 and 20 °C (Kilic, 2009). In a study on drying of chicken meat, the TBARS value was 0.96 mg/kg at 15 °C while it was determined as 1.12 mg/kg at 50 °C (Jiang et al., 2016). It was reported that the increase of curing temperature from 4 to 10 °C increased the TBARS value of pastırma samples from 31.68 to 43.04 μmol MDA/kg (Hazar, Kaban, & Kaya, 2017). The average NPN value of cold-dried slices was 4.26 g/100 g. The amount of non-protein nitrogenous substances such as peptides, amino acids, aldehydes, organic acids and amines increases as a result of proteolysis in processed meat products (Kaban, 2009; Kaban & Kaya, 2011; Toldrá, 1998; Virgili, Saccani, Gabba, Tanzi, & Soresi Bordini, 2007). Soyer, Uğuz, and Dalmış (2011) reported that the NPN value increased from 5.01% to 9.17% during pastırma production. Aksu and Kaya (2001a) found that the NPN value changed between 4.03 and 5.25 g/100 g in pastırma samples produced using different starter cultures. Hazar et al. (2017) reported that there was no significant effect of the curing temperature on the NPN value (4.90–5.83 g/100 g) of pastırma samples. A lower NPN value of cold-dried slices as compared to NPN values found in the literature would be in good agreement with the fact that the cold drying process inhibited enzymatic and microbial proteolysis.

3.4. Weight loss and changes in size of cold-dried beef slices Weight loss and the decrease in length, width and thickness of colddried slices are presented in Table 3. The factors had no effect on weight loss of cold-dried slices and the average weight loss was 57%. This was due to the drying of samples to the same moisture content at all temperatures (10, 15 and 20 °C) and air flow rates (1, 2, 3 and 4 m/s). The length of samples dried at 10 °C decreased more (P < .01) than those of other samples. In samples dried at 10 °C with a shorter drying time, there might be further shortening in their protein structure because of the rapid removal of water. The greatest decrease in thickness (30.22%, P < .01) was determined in samples dried at 20 °C. According to these results, it was determined that cold-dried slices were shorter and thicker at the low temperature and high air flow rate, which ensured fast drying, because of shortening of the protein fibers. During drying, the decrease in size of meat may be sourced from the volume of the diverging water, the mobility of the solid matrix, and a high drying rate (Clemente, Bon, Sanjuán, & Mulet, 2009). In a study, it was found that the volume of samples dried faster with cold air (15 °C, 1.5 m/s and 50–76% relative humidity) decreased more than that of samples dried by a natural method (12–19 °C and 55–85% relative humidity) for the same drying time (Zhang, Liu, Wang, Liu, & Gao, 2017). On the contrary, it was reported that drying temperature (5, 10, 15 and 20 °C) had no effect on the change in size of pork samples (Clemente, Bon, Sanjuán, & Mulet, 2009).

3.3. Color values of cold-dried beef slices L*, a* and b* values of cold-dried slices are given in Table 2. L* and b* values of cold-dried slices significantly (P < .01) decreased with increasing temperature. This result might be due to the loss of myoglobin pigment during drying and the dark-colored compounds formed by the Maillard reaction. The color of meat can be better protected when the drying process is carried out at as low a temperature as possible. Lim, Lee, Seo, and Nam (2012) reported that the L*, a* and b* values of meat dried in hot air were lower than those of meat dried naturally in the sun. In another study, it was found that the L* and b* values of meat samples dried at 8–10 °C decreased as the drying time increased (Teixeira, Pereira, & Rodrigues, 2011). In a study by Mujaffar and Sankat (2015), the Hunter L value decreased from 52.9 to 46.2 when the drying temperature of fish slices increased from 30 to 60 °C and the Hunter b value decreased from 15.2 to 11.1 when the drying temperature increased from 40 to 50 °C. According to these results, keeping the drying temperature of beef slices as low as possible causes a smaller change in color values. Because, color development in dried meat products is related to the chemical structure and quantity of myoglobin pigment in meat and the increase in temperature can cause more loss of myoglobin pigment (King & Chen, 1998; Toldrá, 2011). L* and a* values of the cold-dried slices were not affected (P > .05)

3.5. Cutting force and toughness values of cold-dried slices The cutting force and toughness values were significantly (P < .05, P < .01) affected by drying temperature and air flow rate (Table 3). The cutting force and toughness values for drying at low temperature and high air flow rate, which causes rapid drying, were higher. This might be due to the fact that the structure is harder and tighter because of the rapid drying as a result of the interaction of amino acids with water decreasing, and amino acids interacting with each other. Product composition and production processes are important factors affecting the textural properties of meat products. In particular, myofibrillar proteins (actin and myosin), intramuscular connective tissue and perimysium play an important role in the absorption of water and the mechanical strength of muscle fibers (Laopoolkit & Suwannaporn, 2011). During the drying process, significant changes in meat proteins can occur and a significant decrease in the water content of the meat can be observed (Akköse et al., 2018; Aktaş, Aksu, & Kaya, 2005; Lorenzo, 2014). A very short or very long drying time also causes a significant deterioration in the textural properties of the product. These products are described as very soft or very hard and brittle (Konieczny, Stangierski, & Kijowski, 2007). In agreement with our study, Jiang et al. (2016) reported that the cutting force value of samples dried at 15 °C was higher than that of samples dried at 50 °C. This difference may result from the decomposition of collagen and connective tissue at high temperature. The cutting force values of pork samples vacuum-dried at 95 and 100 °C were determined as 48.76 and 49.95 N respectively, and it was reported that high temperature led to denaturation of proteins causing water to leak from the cells and consequently, an increased cutting force (Laopoolkit & Suwannaporn, 2011). Lim et al. (2012) also reported that hot air-dried samples had higher cutting force values than sun-dried samples.

Table 2 Color characteristics of cold-dried beef slices ( ± standard error). L⁎

a⁎

b⁎

Temperature (T, °C, n = 8) 10 27.27a ± 0.24 15 25.62b ± 0.24 20 25.12b ± 0.32 Significance ⁎⁎

11.69a ± 0.21 11.34a ± 0.20 11.01a ± 0.22 NS

7.80a ± 0.15 7.09b ± 0.27 6.71b ± 0.27 ⁎⁎

Air flow rate (A, m/s, n = 6) 1 25.70a ± 2 25.87a ± 3 25.91a ± 4 26.53a ± Significance NS T×A NS

10.98a 11.14a 11.43a 11.84a NS NS

6.74b 6.84b 7.17b 8.05a ⁎⁎ NS

0.43 0.59 0.50 0.47

± ± ± ±

0.33 0.21 0.17 0.22

± ± ± ±

0.29 0.27 0.27 0.20

a,b

Means with different letters within the column indicate differences. NS Not Significant (P > .05). ⁎ P < .05. ⁎⁎ P < .01. 39

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Table 3 Physical properties of cold-dried beef slices ( ± standard error). Weight loss (%)

Decrease in length (%)

Decrease in width (%)

Decrease in thickness (%)

Cutting force (N)

Toughness (N×s)

Temperature (T, °C, n = 8) 10 56.73a ± 0.44 15 57.56a ± 0.61 20 56.70a ± 0.49 Significance NS

25.92a ± 0.73 22.89b ± 0.92 20.83c ± 0.73 ⁎⁎

33.65a ± 0.97 33.38a ± 0.84 33.52a ± 0.79 NS

28.47b ± 0.93 28.78b ± 1.26 30.22a ± 0.94 ⁎⁎

49.54a ± 1.17 48.84a ± 1.16 47.10b ± 0.48 ⁎

244.65a ± 10.14 227.47b ± 8.93 201.66c ± 6.99 ⁎⁎

Air flow rate (A, m/s, n = 6) 1 56.79a ± 2 56.22a ± 3 56.93a ± 4 58.03a ± Significance NS T×A NS

20.47c 22.53b 24.27a 25.58a ⁎⁎ NS

30.21b 33.76a 35.40a 34.70a ⁎⁎ NS

32.79a 30.64b 26.38c 26.82c ⁎⁎ NS

46.45b 46.85b 49.90a 50.77a ⁎⁎ ⁎⁎

202.45b 205.00b 241.92a 249.01a ⁎⁎ ⁎⁎

0.46 0.44 0.71 0.61

± ± ± ±

0.78 1.21 1.11 0.89

± ± ± ±

0.82 0.42 0.38 0.18

± ± ± ±

0.48 0.44 0.45 0.58

± ± ± ±

1.34 0.76 0.74 0.80

± ± ± ±

3.75 10.52 10.62 9.50

a,b,c

Means with different letters within the column indicate differences. NS Not Significant (P > .05). ⁎ P < .05. ⁎⁎ P < .01.

values (< 0.96) and therefore it loses its vitality due to increasing temperature during pasteurization and decreasing water activity during drying (Hazar et al., 2017; Kaban, 2009). The Micrococcus/Staphylococcus count of cold-dried slices was found to be higher than that for other microorganism groups. Kaban (2009) reported that catalase-positive cocci, mainly Micrococcaceae, are the predominant microorganisms in dried meat products. It has been reported that catalase-positive cocci show better growth than LAB as the pH value of dried meat products is suitable, prevents oxidative rancidity and contributes to the formation of aroma compounds by proteolytic and lipolytic activity (Kaban, Kaya, & Lücke, 2012). LAB counts of cold-dried slices were found to vary between 1.00 and 2.97 log cfu/g, and these low counts might be due to high oxygen exposure. The count of LAB, which are responsible for fermentation, varied over a wide range in studies on dried meat products (Aksu & Kaya, 2001b; Diler et al., 2008; Petit et al., 2014). The microbial counts in cold-dried slices were lower than those counts in traditionally dried meat products. It was determined that Micrococcaceae (3–7 log cfu/g) were the predominant microorganisms in cecina samples (García, Zumalacarregui, & Diez, 1995). TAMB, LAB and yeast-mold counts on the commercially available biltong samples were found to range between 6.2 and 9.7, 5.7–7.8 and 3.2–7.7 log cfu/ g, respectively (Petit et al., 2014). Micrococcus/Staphylococcus, LAB and yeast-mold counts in pastırma samples obtained from 14 different producers were found to be between 5.28 and 7.69, 3.30–7.90 and 2.30–6.42 log cfu/g, respectively, and Enterobacteriaceae count was

3.6. Microbiological quality of cold-dried slices All microbiological characteristics, including total aerobic mesophilic bacteria (TAMB), total psychrophilic bacteria (TPB) and Micrococcus/Staphylococcus counts of cold-dried slices were significantly (P < .01) affected by drying temperature and air flow rate. Nevertheless, while LAB and yeast-mold counts were significantly affected (P < .01) by drying temperature, they were not affected (P > .05) by air flow rate (Table 4). It was determined that the overall microbial counts of the dried slices increased as the temperature increased from 10 to 20 °C because the ambient temperature was more suitable for the growth of microorganisms. TAMB, TPB and Micrococcus/Staphylococcus counts did also increase with the increase of air flow rate that might be related to the increase of the amount of oxygen. It was reported that TAMB (3.2 log cfu/g), TPB (2.8 log cfu/g) and yeast-mold (3.4 log cfu/g) counts were highest in rainbow trout samples dried at 20 °C and the microbiological quality decreased as the temperature increased from 4 to 20 °C (Kilic, 2009). In another study, similarly, it was determined that TAMB count increased with an increase in drying temperature (from 10 to 15 °C) (Mukherjee, Chowdhury, Chakraborty, & Chaudhuri, 2006). Diler, Güner, Altun, and Ekici (2008) also reported that there was no significant effect of fan speed on the yeast-mold count of dried fish samples. Enterobacteriaceae count was undetectable in all samples dried at different low temperature and air flow rate. This group of microorganisms is higly sensitive to high temperature and low water activity Table 4 Microbiological quality of cold-dried slices ( ± standard error). TAMB (log cfu/g)

TPB (log cfu/g)

Micrococcus/Staphylococcus (log cfu/g)

LAB (log cfu/g)

Yeast-molds (log cfu/g)

Temperature (T, °C, n = 8) 10 2.44c ± 0.09 15 3.29b ± 0.04 20 3.80a ± 0.23 Significance ⁎⁎

1.24b ± 0.09 2.14a ± 0.29 1.89a ± 0.12 ⁎⁎

2.57c ± 0.15 2.94b ± 0.12 3.49a ± 0.22 ⁎⁎

1.45c ± 0.14 1.79b ± 0.17 2.40a ± 0.18 ⁎⁎

2.23b ± 0.21 2.12b ± 0.07 2.76a ± 0.09 ⁎⁎

Air flow rate (A, m/s, n = 6) 1 2.75b ± 0.20 2 3.29a ± 0.25 3 3.26a ± 0.35 4 3.40a ± 0.30 Significance ⁎⁎ T×A ⁎⁎

1.57b 1.54b 1.76b 2.14a ⁎⁎ ⁎⁎

2.73b 3.08a 3.01a 3.18a ⁎⁎ ⁎⁎

1.94a 1.68a 2.05a 1.84a NS ⁎⁎

2.52a ± 0.15 2.38ab ± 0.17 2.17b ± 0.27 2.41ab ± 0.17 NS ⁎⁎

± ± ± ±

0.17 0.22 0.31 0.30

± ± ± ±

0.05 0.10 0.34 0.35

TAMB: Total aerobic mesophilic bacteria; TPB: Total psychrophilic bacteria; LAB: Lactic acid bacteria. a,b,c Means with different letters within the column indicate differences. NS Not Significant (P > .05) ⁎⁎ P < .01. 40

± ± ± ±

0.13 0.23 0.36 0.25

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Table 5 Sensorial scores of cold-dried slices ( ± standard error). Appearance Temperature (T, °C, n = 8) 10 6.83a 15 5.94b 20 6.16b Significance ⁎⁎ Air flow rate (A, m/s, n = 6) 1 5.86b 2 6.34a 3 6.63a 4 6.42a Significance ⁎⁎ T×A NS

Color

Odor

Flavor

Structure

Overall acceptability

± 0.13 ± 0.16 ± 0.19

6.83a ± 0.12 5.83b ± 0.12 5.46b ± 0.26 ⁎⁎

6.71a ± 0.16 5.58b ± 0.13 5.05c ± 0.13 ⁎⁎

6.97a ± 0.11 5.63b ± 0.12 5.87b ± 0.08 ⁎⁎

6.29a ± 0.10 5.99ab ± 0.23 5.80b ± 0.12 ⁎

6.69a ± 0.15 6.02b ± 0.24 6.13b ± 0.10 ⁎⁎

± ± ± ±

5.84a 5.81a 6.21a 6.30a NS NS

5.57b ± 0.45 5.96a ± 0.36 5.86ab ± 0.35 5.73ab ± 0.15 NS ⁎

6.00a 6.19a 6.32a 6.12a NS NS

6.04a 6.00a 6.19a 5.86a NS ⁎⁎

6.19b 6.27b 6.61a 6.05b ⁎⁎ ⁎⁎

0.19 0.13 0.18 0.33

± ± ± ±

0.33 0.32 0.35 0.27

± ± ± ±

0.38 0.23 0.28 0.22

± ± ± ±

0.20 0.13 0.16 0.28

± ± ± ±

0.18 0.10 0.22 0.34

a,b,c

Means with different letters within the column indicate differences. NS Not Significant (P > .05) ⁎ P < .05. ⁎⁎ P < .01.

average TAMB, TPB, Micrococcus/Staphylococcus, LAB and yeast-mold counts were 3.18, 1.76, 3.00, 1.88 and 2.37 log cfu/g, respectively. As a result of sensory evaluation, it was concluded that cold-dried slices performed at 10 °C and 3 m/s had the highest overall acceptability score.

below the detectable level (< 2 log cfu/g) (Öz, Kaban, Bariş, & Kaya, 2017). 3.7. Sensory quality of cold-dried slices The appearance, color, odor, flavor, structure and overall acceptability scores of cold-dried slices at different temperature and air flow rates are given in Table 5. While all sensorial properties of cold-dried slices were significantly affected (P < .05, P < .01) by drying temperature, only the appearance and overall acceptability were affected (P < .01) by air flow rate. All sensorial properties of slices cold-dried at 10 °C had significantly higher scores, and these scores showed a similar decrease as the temperature increased. This may be due to the browning of the meat due to increased activity of endogenous enzymes in the meat with increasing temperature, the formation of undesirable taste and aroma compounds, and the softer structure because of slow drying at 20 °C. It was reported that fermented goat meat sausages were sensorially less favorable as the drying temperature increased (Mukherjee et al., 2006). Contrarily, Jiang et al. (2016) reported that the color, aroma and taste scores of samples dried at 15 °C were lower than those of samples dried at 50–65 °C. In another study in which pork was dried at high temperatures (40, 50 and 60 °C), the temperature increase caused a significant increase in structure and overall acceptability scores (Choi et al., 2015). The appearance and odor scores of slices dried at 1 m/s were lower than those of samples dried at 2, 3 and 4 m/s. The slices dried at low air flow rate might be darker than the other samples, although not sensorially noticed. The reason for a low odor score might be the insufficiency of air flow rate in the removal of the dense raw material odor. In addition, the overall acceptability score of slices cold-dried at 3 m/s was significantly higher than that of slices cold-dried at 4 m/s. This may be due to the high air flow rate (4 m/s) increasing oxygen exposure and hence lipid oxidation.

Acknowledgements The authors wish to share their acknowledgements for the financial support provided for the project entitled “Designing a cold dryer for producing a minimally processed dried meat and determining the drying and quality characteristics of dried meat product” under project no: FBA-2016-1187 by Akdeniz University Scientific Project Commision. References Akköse, A., Kaban, G., Karaoğlu, M. M., & Kaya, M. (2018). Characteristics of pastırma types produced from water buffalo meat. Kafkas Universitesi Veterinerlik Fakültesi Dergisi, 24(2), 179–185. Aksu, M. I., & Kaya, M. (2001a). The effect of starter culture use in pastırma production on the properties of end product. Turkish. Journal of Veterinary and Animal Science, 25, 847–854. Aksu, M. I., & Kaya, M. (2001b). Erzurum piyasasında tüketime sunulan pastırmaların bazı fiziksel, kimyasal ve mikrobiyolojik özellikleri. Turkish. Journal of Veterinary and Animal Science, 25, 319–326. Aktaş, N., Aksu, M. I., & Kaya, M. (2005). Changes in myofibrillar proteins during processing of pastirma (Turkish dry meat product) produced with commercial starter cultures. Food Chemistry, 90, 649–654. Andrés, A. I., Adamsen, C. E., Møller, J. K. S., Ruiz, J., & Skibsted, L. H. (2006). Highpressure treatment of dry-cured Iberian ham. Effect on colour and oxidative stability during chill storage packed in modified atmosphere. European Food Research and Technology, 222, 486–491. Anonymous (2012). Türk Gıda Kodeksi Et ve Et Ürünleri Tebliği (2012/74). Ankara: Gıda, Tarım ve Hayvancılık Bakanlığı, 5 Aralık 2012 tarih ve 28488 sayılı Resmi Gazete. AOAC (2000). Association of Official Analytical Chemists, official methods of analysis (17th ed.). Washington DC: AOAC. Aristoy, M. C., & Toldrá, F. (1998). Concentration of free amino acids and dipeptides in porcine skeletal muscles with different oxidative patterns. Meat Science, 50, 327–332. Aykın, E., & Erbaş, M. (2016). Quality properties and adsorption behavior of freeze-dried beef meat from the Biceps femoris and Semimembranosus muscles. Meat Science, 121, 272–277. Aykın-Dinçer, E., & Erbaş, M. (2018). Drying kinetics, adsorption isotherms and quality characteristics of vacuum-dried beef slices with different salt contents. Meat Science, 145, 114–120. Aykın-Dinçer, E., & Erbaş, M. (2019). Cold dryer as novel process for producing a minimally processed and dried meat. Innovative Food Science and Emerging Technologies. https://doi.org/10.1016/j.ifset.2019.01.006 In Press. Calicioglu, M., Sofos, J. N., Samelis, J., Kendall, P. A., & Smith, G. C. (2002). Destruction of acid- and non-adapted Listeria monocytogenes during drying and storage of beef jerky. Food Microbiology, 19, 545–559. Calicioglu, M., Sofos, J. N., Samelis, J., Kendall, P. A., & Smith, G. C. (2003). Effect of acid adaptation on inactivation of Salmonella during drying and storage of beef jerky treated with marinades. International Journal of Food Microbiology, 89, 51–65. Chabbouh, M., Hajji, W., Ahmed, S. B. H., Farhat, A., Bellagha, S., & Sahli, A. (2011).

4. Conclusion Consumers are attracted to dry snack foods for their convenience, taste, easy transportation and storage. This study showed that a beef snack product can be produced by using a cold dryer at 10–20 °C and 1–4 m/s. It was determined that cold-dried beef slices were in the class of intermediate moisture food; the average moisture content was 40%, and the water activity value was 0.89. The pH, TBARS and NPN values of cold-dried meat slices were 5.74, 48.25 μmol MDA/kg and 4.26 g/ 100 g, respectively. The low drying temperature positively affected the color of the cold-dried slices. In addition, the microbiological quality of slices dried at low temperature and low air flow rate was high and 41

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